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Testing the Effects of Helium Pressurant on Thermodynamic Vent System Performance with Liquid HydrogenIn support of the development of a zero gravity pressure control capability for liquid hydrogen, testing was conducted at the Marshall Space Flight Center using the Multipurpose Hydrogen Test Bed (MHTB) to evaluate the effects of helium pressurant on the performance of a spray bar thermodynamic vent system (TVS). Fourteen days of testing was performed in August - September 2005, with an ambient heat leak of about 70-80 watts and tank fill levels of 90%, 50%, and 25%. The TVS successfully controlled the tank pressure within a +/- 3.45 kPa (+/- 0.5 psi) band with various helium concentration levels in the ullage. Relative to pressure control with an "all hydrogen" ullage, the helium presence resulted in 10 to 30 per cent longer pressure reduction durations, depending on the fill level, during the mixing/venting phase of the control cycle. Additionally, the automated control cycle was based on mixing alone for pressure reduction until the pressure versus time slope became positive, at which time the Joule-Thomson vent was opened. Testing was also conducted to evaluate thermodynamic venting without the mixer operating, first with liquid then with vapor at the recirculation line inlet. Although ullage stratification was present, the ullage pressure was successfully controlled without the mixer operating. Thus, if vapor surrounded the pump inlet in a reduced gravity situation, the ullage pressure can still be controlled by venting through the TVS Joule Thomson valve and heat exchanger. It was evident that the spray bar configuration, which extends almost the entire length of the tank, enabled significant thermal energy removal from the ullage even without the mixer operating. Details regarding the test setup and procedures are presented in the paper. 1
Document ID
20060048241
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Flachbart, R. H.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Hastings, L. J.
(Alpha Technology Huntsville, AL, United States)
Hedayat, A.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Nelson, S.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Tucker, S.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2006
Subject Category
Fluid Mechanics And Thermodynamics
Meeting Information
Meeting: AIAA Joint Propulsion Conference and Exhibit 2006
Location: Sacramento, CA
Country: United States
Start Date: July 9, 2006
End Date: July 12, 2006
Distribution Limits
Public
Copyright
Other

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